Correction to This Article
Previous versions of this article, in describing the experience of a traveler flying from London's Heathrow Airport to the Washington area, incorrectly said that the destination was Reagan National Airport. The flight was to Dulles International Airport. This version has been corrected.

Travelers described heightened security and new restrictions at the end of the busy holiday weekend, including extensive searches before they were allowed to board flights coming from overseas and limits to their movements as the planes approached the United States.

On Friday, a Nigerian man allegedly tried to set off an explosive on a flight from Amsterdam and bound for Detroit, resulting in additional security measures on U.S.-bound flights. On Sunday, on the same Northwest flight, a man was removed from the plane after becoming disruptive and locking himself in a restroom. The man, also a Nigerian, according to wire reports, later was found to have no weapon or explosives, and investigators concluded that he posed no threat.

Passengers flying into the United States from abroad should expect such additional security precautions as increased screening at gates, pat-downs and bag searches, the Transportation Security Administration said late Sunday. "During flight, passengers will be asked to follow flight crew instructions, such as stowing personal items, turning off electronic equipment and remaining seated during certain portions of the flight," the TSA said. Passengers leaving international airports should allow an extra hour, the agency advised.

Security checkpoints for those departing from U.S. airports remain the same, although passengers might notice additional steps and should allow extra time before their flight, the TSA announcement said.

Jed Hathaway, who was traveling from Sioux City, Iowa, to Ashburn, said security workers went through his wallet, flexing it and checking to see that nothing was in it other than cash and credit cards.

"The only difference was when we were boarding, we were patted down a second time," said Becky Nolin, 25, a charter school teacher who was returning home to Capitol Hill from Los Angeles.

Many domestic passengers chalked up long lines to snowstorms and holiday travel and said they were surprised that security measures did not seem more rigorous. Passengers arriving on international flights, however, described tighter security, with variations from flight to flight.

The TSA had announced Friday that passengers might notice additional security measures. "These measures are designed to be unpredictable, so passengers should not expect to see the same thing everywhere," Homeland Security Secretary Janet Napolitano said in a statement.

The TSA also uses dogs trained to detect explosives and behavior analysis, among other measures, not all of which are visible to travelers.

Some arriving from Bogota, Colombia, said that security had long been tight there but that they had noticed additional measures.

"It was tougher than the usual in Bogota," said Francisco Chichizola, a 51-year-old systems administrator who began his trip in Lima, Peru, and was returning home to Springfield.

Leslie Stone said she and her husband weren't allowed to keep water in sippy cups for their 4-year-old and 2-year-old, unlike the usual routine in Bogota, where they often fly to visit family.

A traveler from London's Heathrow Airport described a second search, including a frisking and close examination of all carry-on bags. In the final hour of the flight into Dulles International Airport, passengers were not allowed to leave their seats, and items including pens, books and the airline's pillows had to be stowed.

Passengers on a flight from Tokyo to Dulles also described staying in their seats for the final hour, bag searches and pat-downs.

Fliers couldn't use blankets in the final hour, so the crew "could see everything -- and it was quite cold!" said Mei Levin, who has been traveling on business in China.

Inconvenient, but worth it, many passengers said.

"We lost people in the Lockerbie incident years ago," Hathaway said, "so we understand security and the need for it."